A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
In this posting:
[1] Uganda: central and eastern regions
[2] Nepal: resistance breeding
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[1] Uganda: central and eastern regions
Date: Wed 8 Dec 2010
Source: Daily Monitor [edited]
<http://www.monitor.co.ug/Magazines/Farming/-/689860/1068138/-/2madbyz/-/>
Tomato bacterial wilt strikes again
[In Mukono district], tomato plantations started to wither away.
Godfrey Sseruwu, Mukono Zonal Agricultural Research Institute (Muzardi), identified the disease as tomato bacterial wilt. He said the disease is caused by a soil-borne bacterium, _Ralstonia solanacearum_, which cannot be controlled by spraying.
Mr Sseruwu said the disease is currently a great threat to tomatoes mostly in the central and eastern regions of Uganda. "Once you know that the soils were once affected, don't plant tomatoes there," he advises. He adds, "Whenever you see an affected plant, remove it immediately and burn it."
Sseruwu says farmers can also use tolerant varieties like Tangeru 97, which is currently being evaluated by researchers at Muzardi.
According to him, the variety can be affected but not as much as other common varieties.
Tomatoes are the most popular vegetable used by almost everybody daily and dominate home gardens. Mr Sseruwu says farmers ought to seek advice from extension services when they spot any type of disease.
[Byline: Joseph Miti]
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[2] Nepal: resistance breeding
Date: Mon 6 Dec 2010
Source: FreshPlaza, Republica (Nepal) report [edited] <http://www.freshplaza.com/news_detail.asp?id=72854>
Nepali farm develops disease-resistant tomatoes
Gorkha Seed Company has developed 9 varieties of disease-resistant and heat-tolerant tomatoes and is making final preparations to introduce them into the market. "The varieties we have developed are bacteria-resistant and withstand hot climate," senior scientist Dr Kedar Budhathoki said.
The research is currently being undertaken in Lalitpur [district].
"Farmers can produce at least 10 kg [22 lb] per plant even under worst conditions, with temperatures as high as 40 deg C [104 deg F],"
said Budhathoki.
"We are planning to export seeds of these varieties to India and Bangladesh where the climate is hot and the possibility of bacteria attack is high," the company said.
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[Bacterial wilt (BW) caused by _Ralstonia solanacearum_ is one of the major diseases of tomato and other solanaceous crops (including potato and aubergine). It is most severe in tropical and subtropical areas with high rainfall and warm temperatures. Symptoms on tomato include wilting of the youngest leaves, which may recover temporarily during cooler evenings; eventually the whole plant wilts permanently, roots and lower portion of the stem develop browning of the vascular system, invaded roots may rot, and plants may die.
The bacteria are spread by mechanical means (including insects), contaminated equipment, infected plant material, soil, and water.
They can survive in soil on plant debris or roots of hosts. Some weeds and volunteer crop plants may serve as pathogen reservoirs.
Disease management is difficult, relying mostly on exclusion from new areas and use of certified clean tomato explants for planting. Some cultural methods (such as crop rotation), control of pathogen reservoirs, and phytosanitary measures may be used. Grafting susceptible tomato varieties onto rootstocks of resistant aubergine lines is widely practiced in some Asian countries. Tomato varieties with some genetic resistance/tolerance exist, but due to the different strains of the pathogen may not be suitable for all regions. Therefore, breeding programmes to develop resistant tomato varieties suitable for local conditions, like the one in Nepal, are needed.
_R. solanacearum_ affects more than 200 plant species including important crops such as banana, potato, peanut and a number of vegetables. _R. s._ has been classified into various races and biovars active under different climatic conditions and affecting different hosts.
Maps
Uganda:
<http://unimaps.com/uganda/mainmap.gif> and <http://healthmap.org/r/0ivM> Uganda districts:
<http://en.wikipedia.org/wiki/Districts_of_Uganda>
Nepal:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/nepal_pol90.jpg> and <http://healthmap.org/r/0ivN> Nepal regions and districts:
<http://www.un.org.np/reports/maps/npcgis/NatBio00004.jpg> and <http://ncthakur.itgo.com/map04.htm>
Worldwide distribution of _R. solanacearum_ race 1 (updated July 2008):
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum/PSDMSO_map.htm>
Worldwide distribution of _R. solanacearum_ race 3 (updated July 2008):
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum_race3/PSDMS3_map.htm>
Pictures
Bacterial wilt symptoms on tomato plants:
<http://aggie-horticulture.tamu.edu/publications/tomatoproblemsolver/root/images/photos/bac_wilt1.jpg>,
<http://plantpath.ifas.ufl.edu/rsol/images/Modules/Sptme2_BWilt.gif>, and <http://www.lane-ag.org/osu/Tomato/othertomato/Tomato--Bacterial-Wilt--Ral.jpg>
Browning of vascular system:
<http://erec.ifas.ufl.edu/tomato-scouting-guide/images/diseases/bacterial-wilt112.JPG>
Bacteria emerging from wilt affected tomato stem:
<http://plantpath.ifas.ufl.edu/rsol/images/Modules/Stalkooze.gif> and <http://www.lane-ag.org/osu/Tomato/othertomato/bacterial-ooze.jpg>
Links
Information on bacterial wilt of tomato:
<http://www.avrdc.org/pdf/tomato/bacterial_wilt.pdf>,
<http://plantpath.ifas.ufl.edu/rsol/trainingmodules/bwtomato_module.html>,
<http://erec.ifas.ufl.edu/tomato-scouting-guide/diseases/bacterial-wilt.shtml>,
and via
<http://www.oisat.org/pests/diseases/bacterial/bacterial_wilt.html>
_R. solanacearum_ wilts, general information:
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum/PSDMSO_ds.pdf>
Diagnosis and description of _R. s._ races:
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum/pm7-21(1)%20PSDMSO%20web.pdf>
Description and taxonomy of _R. solanacearum_:
<http://expasy.org/sprot/hamap/RALSO.html>,
<http://www.uniprot.org/taxonomy/305>, and via <http://www.bacterio.cict.fr/qr/ralstonia.html>. - Mod.DHA]
[see also:
Brown rot, potato - Lesotho: (MS, TT) 20100221.0591 Bacterial wilt, eggplant - India: (KA) control 20100106.0063
2009
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Brown rot, potato - Australia: (QLD), new strain 20090821.2958
2008
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Brown rot, potato - Ireland 20081028.3401 Brown rot, potato - Russia: (IRK) ex China 20080820.2595 Brown rot, potato - Mauritius: 1st report 20080515.1629 Potato diseases - India: (West Bengal) 20080206.0477
2007
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Moko disease, banana - UK: British Virgin Islands, alert 20071112.3676 Brown rot, potato - Ireland: 1st report 20071022.3438 Moko disease, banana - St Vincent & the Grenadines 20070606.1825 Moko, Bugtok, blood diseases, banana: research 20070513.1524
2005
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Bacterial wilt, potato - Egypt 20050519.1378 and older items in the archives]